What does the poet means by "warmth" of the cricket's song in the poem "On the Grasshopper and Cricket" by John Keats?

In this poem, Keats identifies the grasshopper and the cricket with "the poetry of earth." The grasshopper's song continues when the other animals are parched with heat, and the cricket sings when they are shivering with the onslaught of "frost." When Keats speaks of the "warmth" of the cricket's song, then, he is speaking metaphorically, presenting this warmth as a contrast to the frost and cold which "has wrought a silence" over everything else. Despite this cold, the cricket's song increases in warmth. This emphasizes the idea that the song of the cricket, and its summer counterpart, the grasshopper, is a constant; in intensifying its "warmth" as the cold weather sets in, the cricket maintains a harmonic balance in nature. Metaphorically, too, this "warmth" suggests fondness and goodwill. As long as the warmth of the Cricket's song continues, countering the chill of winter, the "poetry of the earth," likewise, lives throughout the year.